Circuit breaker



March 7, 1939. G. E. wHlTr-:HEAD

CIRCUIT BREAKER 2 Sheets-Sheet 1 Filed Maron 22, 1938 nv Q u A INvENm lHG2.

GHOR GE E WHITEHEAD BY v Www# am w ATTORXEYS March 7, 1939.

' G. EQWHITEHEAD CIRCUIT BREAKER Filed March 22, 19158 2 Sheets-Sheet 2...4:35 ya" v /1 fr! iiiiiiii t nlllllldlrlfrrl.

INVENTOR GEORGE E. WHITEIEAD By ATTORNEYS Patented Mar. 7, 1939 UNITEDSTATES PATENT OFFICE CIRCUIT BREAKER,

Application March 22, 1938,A Serial No. 197,449 In Great Britain May 7,1937 1 Claim.

This invention relates to electrical switches or circuit breakers. andmore particularly the contacts thereof. The invention comprisesmodiiicationsv of the contact arrangements described in thespecifications of Patent Nos. 1,992,109 granted Feb. 19, 1935, and2,032,241 granted Feb. 25, 1936.

According to the present invention the main current carrying fixedcontact is of the resilient sleeve type and is carried at the mouth of ametal housing whilst the main current carrying moving contact is in theform of a plug, the arrangement so far set forth being as shown in Fig.3 of the specification of Patent No. 2,032,241 except that the resilientsleeve contact may be of any other type than that forming the subject ofPatent No.

2,032,241, whilst there need be no free oil channels in the main plugContact. Furthermore there are essentially provided fixed and movingauxiliary arcing contacts of which the moving arcing contact is a springurged plunger carried in an axial bore of the main plug contact andadapted to make buttng engagement with a fixed arcing contact surfacewithin the metal housing. The arrangement is such that during theclosing and opening movements of the circuit breaker the arcing contactsrespectively engage before and separate after the main contacts. Themetal housing is provided with openings for equalizing pressure withinit when the contacts open and close.

The aforesaid arcing plunger may have a relatively free slidingengagement with respect to the main current carrying plug, since it onlyhas to carry the arc current. The moving plunger may i have an extensionprojecting from the main current carrying member which projection may beconnected if desired by a exibie conductor to the main current carryingmember or to the bridge of the circuit breaker if of the double-breaktype. The spring of said plunger may be housed Within the main currentcarrying plug or contact member.

In an arrangement which is alternative to that set forth in thepreceding paragraph and which is particularly suitable for heavy currentcircuit breakers, the spring which urges the arcing plunger may beexternal to the main plug contact and may be duplicated and providedwith guide rods, whilst said main plug carries a resilient sleevecontact, preferably in accordance with Patent No. 2,032,241 aforesaid,in which the arcing plunger is slidable.

To enable the invention to be more clearly understood reference will noWbe made to the accompanying drawings in which- Figure 1 is a sectionalelevation oi one form of the circuit breaker contacts in accordance withthe invention showing the contacts in the fully closed position and Fig.2 is an elevation showing the contacts in the open position.

Figs. 3 and 4 are views similar to Figs. 1 and 2 of another form of thecontacts in` accordance with the invention.

Fig. 5 is a fragmentary horizontal section, on l0 an enlarged scale,taken on the line 5 5 in Fig. 1.

Referring rst to Figs. 1 and 2 of the accompanying drawings, at l isshown one of the fixed contact stems oi a circuit breaker which stem is15 shrouded with insulation 2. Screwed to the lower end of the contactstem l is the tubular housing 3 which at its lower end is enlarged toform an annuiar casing fr for the circularly laminated main; fixedcurrent carrying contact 5 which 20 per se is as described in thespeciiication of Patent No. 2,032,241 aforesaid. As shown in Fig.

5, the contact 5 comprises an annulus of closely packed thin flexiblelaminae 5a, compo-sed preferably of similarly bent strips of copperhaving 25 their inner ends disposed in close relation and forming aresilient wall for engagement with the main current carrying movingcontact a portion of the periphery of which is indicated by the dottedline 5a, to provide a good electrical contact 30 therewith. The outerends of these laminae abut against the surrounding wall 3a of a recessformed in the lower end of the housing 3. The laminae 5a may beseparated by interposed similarly bent but relatively shorter laminae 5bof 35 phosphor bronze or steel.

With the resilient socket contact 5 co-operates the main currentcarrying moving contact which is in the form of a plug 6 which has adownward extension 'i of larger diameter clamped to the 40 movingcrossbar 8 of the circuit breaker. The moving member 8, 1 is tubular andcarries within its bore the arcing plunger 9 which is urged upwardsrelatively to the main contact 6 by means oi the helical spring l0 whichsurrounds a stem li secured to or forming part of the plunger 9 andextending through the crossbar 8 and having at its lower end a stop l2which limits the upward movement of the plunger 9 relatively to the plug6. It will be appreciated that the plunger 9 is readily removable sothat it can be changed in case the arcing end becomes burnt.

The plunger 9 may be arranged to fit freely in the bore oi the main plug6 and the lower end 55 of the extension II may be connected to thebridge 8 by means of a ilexible conductor.

Secured Within the tubular upper portion 3 of' the metal housing is thefixed arcing contact I3 which conveniently has an enlarged screw--threaded portion I4 so that the fixed arcing plug I3 is readilyinterchangeable in case it may ben come burnt.

The housing 3, 4 is shown disposed Within the shrouding tube I5 ofinsulating material which may be fixed in a perforation in a barrier IGwhich may extend across the oil tank of the circuit breaker.

The housing 3 is provided with a plurality, for example three, of holesII for equalizing the pressure within the housing 3 during the openingand closing of the circuit breaker. The housing 3 acts after the mannerof an explosion pot tending to quench the are which forms between thefixed butt contact I3 and the plunger 9 after the main current carryingplug has been entirely Withdrawn from the resilient sleeve contact 5.

Referring next to Figs. 3 and 4 the arrangement therein illustrated onlydiffers from that shown in Fig. 1 in that in the first place the plunger9 slides in a further resilient sleeve contact I8 carried at the lowerend of the main cur rent carrying plug 6. The sleeve contact I8 ispreferably similar to the sleeve contact 5. In the second place thespring Ill shown in Fig. 1 within the lower portion I of the mainContact plug 6, is replaced by external springs I 9 surrounding headedguide rods 2D attached to a plate 2| xed to the lower end of the plunger9. The arrangement shown in Figs. 3 and 4 is adapted for a heavy currentcircuit breaker. In one example thereof which has been foundparticularly successful the diameter of the main plug was about 1.7inches (4.47 cms.) and the rating of the circuit breaker was 900amperes.

The invention may be applied if desired to circuit breaker arrangementswherein the oil is pumped upwards through the housing 3, 4 duringcircuit breaker opening.

It will be understood that various minor modifications in thearrangement illustrated and described may be made Within the scope ofthe invention.

I claim:

For an electric oil circuit breaker, a ixed metal housing having a maincurrent carrying xed contact of the resilient sleeve type carried at themouth thereof, said housing having at least one hole therein above saidmain xed contact, a rigid butt type arcing contact Within said housingand having its contact surface above said main fixed contact, a mainmoving contact in the form of a plug adapted to cooperate with saidresilient sleeve type contact, said plug contact being tubular, and aspring urged arcing contact in the form oi a plunger carried within thebore of said plug contact and adapted to make and break engagement withsaid fixed arcing contact Within said housing.

GEORGE ETHELBERT WHITEHEAD.

